Thermal cut-out switch



Nov. 17, 1936. F,ITAXNER 2,060,836

THERMAL CUT-OUT SWITCH Filed April 28, 1953 39 I312 I Q INVENTOR Patented Nov. 11, 1936 UNITED STATES PATENT OFFICE THERMAL CUT-OUT SWITCH Frank Taxner, Turtle Creek, Pa. I v Application April 28, 1933, Serial No. 668,355

'29 Claims.

. My invention relates to cut-out switches but more particularly to thermal cut-out switches for general use where temperature control is necessary.

My invention may also be-applied to non-thermal switches, the switch being thrown by a handle or other mechanical means or connections.

- In general the object which I have in view is the provision of a device of this character which is 10 simple and inexpensive to manufacture, durable,

eflicient, and quick-acting in opening and closing.

Other objects appear hereinafter; In the accompanying drawing wherein I have 15 illustrated -a practical embodiment of the principles of my invention, Fig. 1 is a side elevation ofone form of the thermal switch, the same being partly broken away to show operating parts.

Fig. 2 is a plan view of the structure illustrated 20 in Fig. 1.

Fig. 3 is a side elevation showing a modification. Fig. 4 is a detail of one of the bearing sockets shown in Fig. 1.

Fig. 4a is a detail of a modified form of -a bear- 5 being omitted or broken away.

Fig. 9 is a view in perspective of the contact material, the block 8 being attached by the rivets 9 to said brackets.

I and II represent binding posts mounted on the terminal block 8 and insulated therefrom, and I2 are contact buttons mounted on the lower ends of said posts which depend below said block. The buttons may be composed of any good contact material, such as a platinum and silver alloy. The buttons I2 are arranged to contact with similar contact buttons I3 carried by the free endof the 10 spring contact finger or arm I4.

The circuit of the apparatus that is to be protected by my thermal control switch is placed in series with the binding posts l0 and I I in the usual manner, and such circuit is made or broken according to the heat dissipated by the apparatus which controls the movement of the contact finger I4.

Extending laterally of the base I and adjacent to the brackets 4 and 5 are the ears I5 and I6 which serve as supports for mounting the switch inplace.

I1 is a flat bimetal strip and I8 is a flat leaf spring or radius arm of heat-resisting metal superimposed on the strip H. The strip and springare fastened at one end to the inturned flange of the bracket 3 by means of the machine screws I 9. The bimetal strip I1 extends longitudinally of the'base I and its free end, in its normal or cold position rests on the upper surface .of theinturned flange of the bracket 2. The

finger employed in the structure shown in Figs. 7-

Referring first to Figs. 1 and 2, I represents the I base or frame of the device formed with a suitable 45 heat-resisting metal, such as stainless steel; Upon this frame are assembled the parts comprising the thermal switch. The ends of the base I are bent downwardly and then inwardly towards each other to form the opposed brackets 2 and 3. 4 and 5 50 represent brackets extending upwardly from the base I intermediate of its ends, and their upper ends are provided with flanges 6 and 1 extending inwardly towards each other.

The brackets 4 and 5 support the terminal block 8 which may be made of suitable heat resisting spring I8, which may be termed the actuating spring, also extends longitudinally of the base I and is secured by rivets to the bottom of the 'nally of the base I and is pressed to form a rounded pivot 23 on its upper surface which is disposed laterally of the leg and bears from below on the lower surface of the base I. The leg 2| is extendedbeyond the pivot 23 to act as a stop to arrest the lever 20 in the normal position as shown in Fig. 1.

The leg 22 of the lever 20 extends up through an opening in the basev I and terminates in the concaved V-shaped bearing socket 24 in which is engaged the convex V-shaped pivot member 25. The member 25 is held from lateral movement within the socket 24 by the oppositely disposed ears 28 of the socket 24, as shown in Fig. 1. The member 25 is a part of the bracket 2'! to which is attached the contact finger I4 and the jack spring 28.- The jack spring 28 is made of suit- 55 able fiat heat-resisting metal and is attached at its opposite end to a pivot member 29.

The jack spring 29 may be said to be a chord with respect to the radius arm [8 and as the radius arm is rotated through a small arc the chord spring must flex as distance between its ends is shortened.

To secure the jack spring to the bracket 27 and the pivot member 29 its ends are notched out as at 39, so that when said ends are slid into engagement with the members 21 and 29 the tongues 3I struck from said brackets hold the spring snugly against the side portions 32 of the bracket while the ends 33 of the spring extend beyond the bend in the necks of the tongues to hold the spring against lateral displacement. This arrangement forms a secure assembly of the brackets in the jack spring.

The bracket 21 is off-set at 34 to form a suitable surface for mounting the contact finger I4 thereon. The contact finger is secured as by rivets 35 to said bracket but is insulated there from in the usual manner. The end 36 of the bracket is arranged to limit the upward bending movement of the jack spring 29.

The jack spring pivot member 29 has formed thereon a convex or V-shaped portion 31 similar to the pivot member 25 of the bracket 21, and the same is pivotally mounted within the concaved bearing socket 38 of the bracket 39 also shown in Fig. 4, the bracket 39 being fixed to the base I as shown in Fig. l. The cars 26 prevent lateral movement of the pivot-member 29. An extension 40 of the bracket 39 is arranged to engage the upper surface of the base I to limit the downward bending movement of the jack spring 28.

Referring now to Fig. 5, I show a reversal of the pivotal connection of the jack spring shown at 29--3B in Fig. 1, the member 29a attached to the end of the jack spring being formed as the socket while the portion 39a of the bracket 39 is the pivot member received in the socket.

The operation of the switch as illustrated in Figs. 1 and 2 is as follows. The switch is mounted in such manner that its bimetal strip I1 is adjacent the portion of the associated apparatus which is to be protected from overheating, or is otherwise exposed to temperatures which are to be controlled. As the heat is convected, its efiect on the strip I1 is to cause the free end of the latter to swing upwardly or toward the base I, the amount of its deflection being proportional to the temperature to which it is exposed. Such deflection of the strip II flexes the spring I8 and thus causes the angular lever 20 to swing clockwise on its pivot 23 which slides slightly on the under surface of base I, the spring I8 acting as a radius arm for the pivotal movement of the lever. As a result of this movement of the lever its leg' 22 swings clockwise in Fig. 1 thus bowing the jack spring 28 downwardly, the stop 36 on the bracket 21 preventing an upward bowing of the jack spring. The initial flexing of the jack spring results in a sliding movement of the contact buttons I3 relative to the contact buttons I2 without breaking contact and as the bimetal strip I'I approaches its maximum bending movement its increased deflection causes the jack spring-to snap into'its position of maximum deflection wherein the extension 40 contacts with the base I, thus snapping the buttons I3 out of contact with the buttons I 2 and thus breaking the circuit.

It is evident that the normal position of the buttons l3 relative to the buttons I2 while the circuit is closed is not the same as is their position just previous to breaking contact. Thus a low-resistance contact between the two pairs of buttons is assured during normal operation of apparatus with the switch closed.

As the bimetal strip cools after the circuit has been broken, it straightens out into its normal position, permitting the spring I8 to swing the lever 20 counterclockwise on its pivot and thereby permitting the jack spring to move toward its straightened position, following the relaxing movement of the strip I'I' until the latter approaches its straightened position, whereupon the jack spring will snap into its straightened position and thus cause the buttons I3 to spring into contact with the buttons I2, thus restoring the circuit.

Referring now to the modification shown in Fig. 3, such parts as are similar to parts already described in connection with Figs. 1 and 2 are designated by like reference numerals while the parts peculiar to Fig. 3 are as follows. 4I represents a stud whose upper end portion 42 is threaded and screwed into a threaded hole at approximately the center of the base I. The lower portion 43 of the stud is squared. 44 represents a shoulder intermediate of the stud which may have flattened perimetral surfaces for the application of a wrench. 45 represents a flat spring with depending ends and the intermediate portion of which is provided with a hole through which the stud extends, and 48 represents a spacing collar mounted on the stud between the base I and the spring, which latter is thus held against the shoulder 44.

41 and 48 represent a pair of oppositely bowed bimetal strips, the centers of which are provided with registering square holes through which the stud 4I extends, thus holding the strips in proper assembled relation and guiding their movements. The ends of the strips rest on the inturned flanges of the brackets 2 and 3. Thus the strips are free to flex while their movements are guided by the stud.

The ends of the spring 45 have secured thereto the brackets 49 and 59 which extend upwardly through openings in the Base I. The upper end of the bracket 49 is provided with a bearing socket 24 similar to the corresponding socket on the lever 20 in Figs. 1 and 2, and the corresponding ends of the spring finger I4 and of the Jack spring 28 are pivotally connected thereto in like manner as in Fig. 1. jack spring 28 is attached to the inturned upper portion of the bracket 50.

The apparatus operates as follows. As the bimetal strips 41 and 4B expand they tend to straighten out and then bow in reverse directions, thus moving the ends of the spring 45 upwardly toward the base I and elevating the brackets 49 and 50 and swinging their upper ends toward each other with the result that the jack spring 28 bends downwardly, thus releasing the pressure of the spring flnger I4 and breaking the circuit. As the bimetal strips cool, they relax and reverse, thus allowing the spring 45 to straighten, and thereby permitting the jack spring to return the spring finger I4 into its contact position.

It will be noted that the ends 01' the spring 45 when in its normal position are flexed downwardly while the jack spring 29 is substantially straight. Thus when as the spring 45 tends to straighten swinging the brackets 49 and 50 toward each other, the jack spring is bowed and The opposite end of the,

i to temperature changes.

I 2,060,886 due to the movement of the brackets the bowthe stud 53 on the end of the multiple diaphragm 54 which in turn is mounted on the end of the tube 55. The tube 55 extends through the back plate of the frame 5| and the fluid whose temperature is to be controlled is admitted through the bore of the tube into the multiple diaphragm, whereby the latter expands and contracts with the expansion and contraction of the fluid due Thus the diaphragm takes the place of and functions as does the bimetal strip I! in Figs. 1 and 2.

Referring now to Figs. '7, 8, 9, and 10, wherein is illustrated an application of the type of switch shown in Fig. 3, 56 is the body of an electric iron and 51 is the cap portion of the same secured thereto by the bolts 58 which may also attach the handle 59. 60 is the heating element which is held in place on top of the body 56 by means of the internal rib 6| of the cap 51. The usual electrical connections for the heating element are employed, the contacts I2 and I3 of the switch being connected in series between the source of supply and the heating element 60 by' the conductors 62.

The body 56 of the iron is provided with the well 63 which is below the open center of the heating element as shown in Figs. 7 and 8. The switch structure is stepped in the well 63, the base plate 64 being provided with the laterally extending ears I 5 and I6 which fit in shallow seats in top of the body 56, so that when the heating element 60 is fastened in position it clamps the plate 64 fixedly in place.

'The stud 4| depending from the plate 64 is longer than that shown in Fig. 3 and has its lower end stepped in a square hole 65 in the floor 66 of the rectangular elevator frame 61. as shown in Fig. 10. The vertical side members of said frame extend upwardly through openings in the plate 64. The cross plate 68 which forms the top of the frame 51 is provided with the threaded hole 69 into which is screwed the lower end of the. suspension bolt 10 which extends up through a loosely fitting hole in the terminal block 8 and also the loosely fitting hole 6| in the cap 51. The upper end of the bolt 10 is provided with an eye through which extends a pin I2 whereby the bolt is pivotally attached in a recess 13 formed in the handle member 14. The nose of the handle member is provided with eccentric bearing surfaces 15 whereby by swinging the handle 14 in a vertical plane and from left to right in Fig. 7, the bolt 10 and with it the elevator frame 61 may be raised.

I6 represents a helical spring coiled about the bolt I6 between the cap 51 and a collar 11 pinned or otherwise secured to the bolt. This spring tends to return the elevator frame 61 to and maintain it in its lowermost position. The ends of the fioor 66 of the elevator frame 61 are provided with the upwardly extending fingers 66a. which, when the frame 61 is raised, engage the ends of the spring 45.

As in Fig. 3, the spring 45 has its center fixed relative to the stud 4| and normally its ends curve downwardly. The brackets 49 and 50 are attached to the ends of the spring 45 as in Fig. 3. Instead of but two bimetal strips 41 and 48 oppositely arranged, as in Fig. 3, in Fig. 7 I have shown a plurality of such pairs below the strips 41 and 48; as at 41d and 48a, and 41b and 48b, all mounted in superimposed relation in the elevator frame 61 and held in proper assemblage between the vertical side members of said frame. It is obvious that by providing a plurality of pairs of bimetal strips I increase the effective deflection resulting from a given temperature differential and thus obtain a more prompt response to a given change of temperature.

It is further obvious that a rotation of the handle 14 on a vertical axis would, by the screw action of the bolt I0, raise or lower the elevator the proper direction to raise the elevatorframe reduces the temperature at which the switch will open, while a reverse rotation of the handle raises said temperature. By providing the cap 51 with a gauge and the handle with a suitable indicating mark or pointer, the user may set the switch to throw off at any predetermined desired temperature.

By throwing the handle 14 from left to right in 'a vertical plane in Fig.- 7, with the pin 12 as an axis, and causing the cam surfaces 15 to ride over the cap 51 the elevator frame 61 may be raised suificiently to cause the fingers 66a to engage the ends of the spring 45, forcing the spring to flex upwardly and thus open the switch. Thus this motion of the handle 14 is used to mechanically throw the switch off and on.

Referring now toFig. 9 I show at Ma a modified form of contact finger which. instead of being bifurcated as in Figs. 1, 2, and 3, comprises a single stem carrying the spring yoke |4b upon which the contact buttons l3 are mounted.

Referring now to Fig. 11 it will be noted that between each of the pairs of opposed bimetal strips 41 and 48, 41a. and 48a, and 41b and 4817, I slidably mount on the stud 4| the fiat plates 18 with which the ends of the bimetal strips contact when they reverse. This provides a better engagement than directly between the ends of the strips. The ends of the plates I8 are rounded to provide a point contact with the strips.

Again I mount above the spring 45 a bimetal strip 19 whose center is fixed on the stud 4| in spaced relation to the spring 45. The bimetal strip 19 is shorter than the strips 41 and 48 and is normally bowed upwardly or away from the spring 45. When it reverses under temperature changes it engages the spring 45 and tends to bow it downwardly while the strip 41 engages the spring adjacent its ends and bows the latter upwardly. The resultant compound flexing of the spring increases the shortening of spring 45 as a result of a given temperature change and thus reduces the temperature differential required to flex the jack spring 28 and open the switch. The ends of strip I9 are rounded to give a point contact.

While I have described my improved thermal switch in use as a cut-out, it is obvious that it may be used as a reversing switch, contacts being provided which will be closed when the contacts illustrated are broken.

It is obvious that two rocking levers, similar to the lever 20 in Fig. 1 could be employed in the structure as set forth under the modification as shown in Fig. '7 to flex the jack spring, the levers being disposed opposite to each other so their ends with which the jack spring is connected will rock toward each other and thus flex the jack spring, these levers being rocked by the flexing of the actuating spring.

This structure is also applicable to the modification of my invention as shown in Fig. 11 whereby the bimetal strip 19 may be reversed so that it will flex downwardly, the ends bearing against the-under surfaceof the base 64 and the two oppositely disposed levers 20 arranged to engage the under surface of the bimetal strip, thereby transmitting a double movement to the brackets 49 and 50 in combination with the bimetal strips 45, 41, etc., thus making the switch more sensitive.

Again, my switch may be constructed without bimetal or other temperature-operated elements, the actuating spring being flexed by mechanical means such as a handle or other attachment or connection.

I claim:-

1. In a thermal cut-out switch, the combination of a base, a leaf spring having one end has-- tened to the base, means actuated by temperature changes arranged to flex said spring, a second leaf spring having one end supported by the free end of the first leaf spring and its other end supported by the base and arranged to be flexed by the flexing of the first leaf spring, and a contact member carried by the second leaf spring and arranged to be held in circuit closing position when said second leaf spring is unfiexed and to be retracted when the second leaf spring is flexed.

2. In a thermal cut-out switch, the combination of a base, a leaf spring having one end fastened to the base, means actuated by temperature changes arranged to flex said spring, a second leaf spring having one end pivotally supported by the free end of the first leaf spring and its other end pivotally supported by the base and arranged to be flexed by the flexing of the flrst leaf spring, and

a contact member carried by the second leaf spring and arranged to be held in circuit closing position when said second leaf spring is unflexed and to be retracted when the second leaf spring is flexed.

3. In a thermal cut-out switch, the combination of a base, a leaf spring having one end fastened to the base, a bimetal element mounted on the base arranged to flex said spring, a second leaf spring having one end supported by the free end of the first leaf spring and its other end supported by the base and arranged to be flexed by the flexing of the first leaf spring, and a contact member carried by the second leaf spring and arranged to be held in circuit closing position when said second leaf spring is unflexed and to be rebracket and having its other end pivotally mounted on a portion of the support, and.a contact member normally held in circuit-closing position by the second leaf spring and arranged to be retracted by the flexing of the latter, whereby when the first leaf spring is flexed by the bimetal strip the second leaf spring is flexed and the contact member is retracted from its closed position.

5. In a thermal cut-out switch, the combination of a support, a bimetal'strip attached at one end to said support, a leaf spring attached at one end to the support and arranged to be flexed by the flexing of the bimetal strip, an angular lever arranged for rocking movement and attached to the free end of said leaf spring, a second leaf spring having one end pivotally connected to the end of said lever, the other end of the second leaf spring being pivotally attached to a portion of the support, and a contact member normally held in circuit-closing position by the second leaf spring and arranged to be retracted by the flex-- ing of the latter, whereby the flexing of the bimetal strip retracts the contact member from its closed position.

6. In a thermal cut-out switch, the combination of a support, a pair of opposed bimetal strips mounted on said support, a leaf spring fixed to said support intermediate of its ends and arranged to be flexed by the flexing of the bimetal strips, a second leaf spring, the ends of which are carried by the ends of the first leaf spring, and which is arranged to be flexed by the flexing of the first leaf spring, and 'a contact member normally held in circuit-closing position by the second leaf spring and arranged to be retracted fromits closed position by the flexing of the latter, whereby the flexing of the bimetal strips retracts the contact member.

'7. In a thermal cut-out switch, the combination of a support, a pair of opposed bimetal strips mounted on said support, a leaf spring fixed to said support intermediate of its ends and arranged to be flexed by the flexing of the bimetal strips, brackets mounted on the ends of said leaf spring, a second leaf spring having its ends pivotally attached to the brackets, and a contact member arranged to be normally held in circuit-closing position by the second leaf spring and to be retracted from its closed position by the flexing of the latter whereby the flexing of the bimetal strips retracts the contact member.

8. In a thermal cut-out switch, thecombination of a base, a leaf spring having one end fastened to the base, means actuated by temperature changes arranged to flex said spring, a second leaf spring having one end supported by the free end of the first leaf spring and its other end supported by the base and arranged to be flexed by the flexing of the first leaf spring, a contact member carried by the second leaf spring and arranged to be held in circuit closing position when said second leaf spring is unflexed and to be retracted when the second leaf spring is flexed, and manually operated means for holding the contact member in open position.

9. In a thermal cut-out switch, the combination of a base, a leaf spring having one end fastened tothe base, a bimetal element mounted on the base arranged to flex said spring, a second leaf spring having one end supported by the free end of the first leaf spring and its other end supported by the base and arranged to be flexed by the flexing of the first leaf spring, a contact member carried by the second leaf spring and arranged to be held in circuit closing position when said 76 second leaf spring is unflexed and to be retracted when the second leaf spring is flexed, and manually operated means for holding the contact member in open position.

10. In a thermal cut-out switch, the combination of a base, a leaf spring having one end fastened to the base, a bimetal element mounted on the base arranged to flex said spring, a second leaf spring having one end supported by the free end of the first leaf spring and its other end supported by the base and arranged to be flexed by the flexing of the first leaf spring, a contact member carried by the second leaf spring and arranged to be held in circuit closing position when said second leaf spring is unflexed and to be retracted when the second leaf spring is flexed, and means for .varying the degree of flex of the bimetal member whereby to regulate the thermal temperature effect to open the switch.

11. In a thermal cut-out switch, the combination of a support, a leaf spring fixed to said support intermediate of its ends, means whereby the flexing of the ends of said leaf spring throws out the switch, and a plurality of pairs of oppositely bowed metal strips arranged to reverse under temperature changes and flex the ends of said spring.

12. In a thermal cut-out switch, the combination of a support, a leaf spring fixed to said 'support intermediate of its ends, means whereby the flexing of the ends of said leaf spring throws out the switch, a plurality of pairs of oppositely bowed bimetal strips arranged to reverse under temperature changes and flex the ends of said spring, and a bimetal strip arranged to flex and engage the leaf spring inside its ends in opposition to the first mentioned bimetal strips.

13. In a cut-out switch, the combination of a base, a leaf spring having one end fastened to said base, a second leaf spring having one end supported by the free end of the first leaf spring and the other end supported by said base, a contact member normally held in circuit-closing position when the second leaf spring is unflexed but arranged to be retracted by the flexing of said springs, and means for flexing the flrstspring to retract said contact member.

14. In a cut-out switch, the combination of a support, a leaf spring mounted on said support, a second leaf spring arranged to normally hold the contact member in circuit closing position and when flexed to retract said member, operative supported by the free end of the first leaf spring and the other end supported by said base, a contact member normally held in circuit-closing position when the second leaf spring is unflexed but arranged to be retracted by the flexing of said springs, means for flexing the first spring to retract said contact member, and means for holding the first spring in its'flexed position.

16. The combination of a-contact member, a spring, a resilient arm mechanically connected to the spring and arranged when said spring is unflexed to hold the contact member in circuit-closing position but when said spring is flexed to hold said contact member in its open circuit position, whereby the flexing characteristics .of the spring do not become impaired while the contact member retains its normal circuit-closed position, and means for flexing said spring.

17. The combination of a contact member, a spring, a resilient arm mechanically connected to the spring and arranged when said spring is unflexed to hold the contact member'in circuit-closing position but when said spring is flexed to hold said contact member in its open circuit position, whereby the flexing characteristics of the spring do not become impaired while the contact member retains its normal circuit-closed position, and thermally activated means for flexing said spring.

18. In a cut-out switch, the combination of a contact member, a jack spring arranged to normally hold the contact member in circuit closing position and when flexed, to retract the contact member, a pair of brackets to which the ends of the jack spring are pivotally connected, and thermally-actuated means for shortening the distance between said brackets whereby to flex the jack spring.

19. In a cut-out switch, the combination of a contact member, a jack spring arranged to normally hold the contact member in circuit closing position and when flexed to retract the contact member, a pair of brackets, socket and pivot members on said brackets and onthe ends of the jack spring whereby the jack spring is supported between the brackets, and thermally-actuated means to shorten the distance between the brackets whereby to flex the jack spring.

20. In a cut-out switch, the combination of a contact member, a jack spring arranged to normally hold the contact member in circuit closing position and when flexed to retract the contact member, a pair of brackets, angular socket and pivot members on said brackets and on the ends of the jack spring whereby the jack spring is supported between the brackets, and thermal- .ly actuated means to shorten the distance between the brackets whereby to flex the jack spring.

21. In a cut-out switch, the combination of a contact member, a jackspring arranged to normally hold the contact member in circuit closposition and when flexed to retract the contact member, a pair of brackets, socket and pivot members on said brackets and on the ends of the jack spring wherebythe jack spring is supported between the brackets, and manually operated ets whereby to flex the jack spring.

23. In a cut-out switch, the combination of a contact member, a jack spring arranged to normally hold the contact member in circuit c ing position and when flexed to retract the contact member, a pair of brackets, angular socket and pivot members on said brackets and on the ends of the jack spring whereby the jack spring is supported between the brackets, and manually operated means to shorten the distance between the brackets whereby to flex the jack spring.

24. The combination .of a contact member, a spring, a resilientarm engaging the spring and means to shorten the distance between the brackarranged when said spring is unflexed to hold the contact member in one position but, when said spring is flexed to hold said contact member in its opposite position whereby the flexing characteristics of the spring do not become impaired while the contact member retains its first mentioned position, and means for flexing said spring.

25. The combination of a contact member, a spring, a resilient arm supported from one end on the spring and arranged when said spring is unflexed to hold the contact member in one position but when said spring is flexed to hold said contact member in its opposite position whereby the flexing characteristics of the spring do not become impaired while the contact member retains its first mentioned position, and means for flexing said spring.

26. The combination of a contact member, a spring, a resilient arm supported from one end on the spring, a contact carried on the other end of the arm, said arm being arranged when said spring is unflexed to hold the contact member in circuit-closing position but when said spring is flexed to hold said contact member in its open circuit position, whereby the flexing characteristics oi. the spring do not become impaired while the contact member retains its normal circuitclosed position, and means for flexing said spring.

27. The combination of a contact member, a radius arm, a spring mounted as a chord with respect to the radius arm and having one end arranged to be operated by the free end of the radius arm, said spring when flexed being arranged to operate said contact member, and means or moving the radius arm to flex said spring.

28. The combination of a contact member, a radius arm, a lever member carried by the free end of the radius arm, a spring pivotally supported at one end on the lever member and by which said contact member is carried, and means for moving the radius arm, the lever thereby rocking the latter causing the spring to become flexed for operating the contact member.

29. The combination of a contact member, a radius arm, a lever carried by the free end of the radius arm, said lever having two legs, one approximately tangent to the radius arm and carrying a pivotal socket and the other being disposed at an angle thereto and carrying a iulcrum point, a spring pivotally supported at one end in the pivotal socket of the lever and by which said contact member is carried, and means for moving the radius arm causing the lever to rock on its fulcrum point thereby increasing the rocking movement of the lever to flex the spring for operating the contact member.

FRANK TAXNER. 

